Because of their stability, electronic properties and fixed molecular structure, which are all derived from the aromatic ring, non-symmetrical biaryl compounds are significantly useful as electronic industry materials, medicines, agricultural chemicals, various functional compounds, and synthetic intermediates of these.
A known method of selective production of non-symmetrical biaryl compounds involves conducting a cross-coupling reaction of an organic boron compound with an organic halogen compound in the presence of a palladium catalyst (Non-patent Literature 1, Patent Literature 1). However, the palladium catalyst and the material, i.e., the organic boron compound, used in this method are both expensive. Therefore, this method is not desirable as an industrial production method. In addition, there is an environmental restriction due to the recent establishment of a boron discharge standard.
Another known cross-coupling method, which carries out a cross-coupling reaction of an organic magnesium compound and an organic halogen compound, does not require as high a cost (Non-patent Literature 2, Patent Literature 2, and Patent Literature 3). This method, which employs an inexpensive organic magnesium compound, generally uses a nickel catalyst or a palladium catalyst. However, nickel catalysts are usually highly toxic, and palladium catalysts are expensive. Therefore, this method ds also not desirable as an industrial production method.
A recent publication disclosed a synthetic method that carries out a cross-coupling reaction of an organic magnesium compound and an organic halogen compound using a safe and inexpensive iron catalyst (Non-patent Literature: 3). Non-patent Literature 3 teaches that the use of iron chloride or acetylacetonato iron as a catalyst ensures a high yield of the reaction of an alkyl magnesium compound and an aryl chloride compound. However, the method of Non-patent Literature 3 is still incapable of carrying out the synthesis of the non-symmetrical biaryl compounds useful for liquid crystalline materials or medical intermediates at a high yield. Therefore, this coupling method is still not desirable as an industrial production method.